Conveyor ovens are used in a variety of industries including the electronics, baking, and painting industries. Generally, conveyor ovens have multiple heating zones through which products pass. The heating zones are thermally isolated from each other by air curtains or other means. Such thermal isolation allows each zone to be maintained at a temperature that differs from other zones in the oven. A particular advantage of conveyor ovens with multiple heating zones is that the products can be heated to different temperatures at different times as they pass through the oven. In all industries that use conveyor ovens, it is important that the ovens behave consistently over time. However, after extended use, the ovens tend to degrade in performance. Some causes of this degradation include dust accumulating on oven fans and/or process bi-products, such as fluxes, accumulating on fans or blocking exhaust ports.
In the electronics industry, conveyor ovens are used to mount integrated circuits and other electronic components to printed circuit boards (PCBs). The multiple heat zones allow the PCB to be gradually raised in temperature so as to prevent thermal stress to the components and the PCB itself. Solder is placed on the PCB at predetermined points where integrated circuits are to be mounted, prior to running it through the oven. As the PCB passes through the heat zones, the solder melts, bonding the integrated circuits to the PCB. Conventionally, prior to a production run, a large number of test PCBs of the same type were passed through the oven under different heating conditions to ensure the temperature profile of the oven matched the requirements of the PCB. Each PCB was analyzed after its pass and the best setting for the oven was determined based on this analysis. This test process resulted in a significant number of test boards being scrapped due to improper heating or overuse. Other industries using conveyor ovens have experienced similar problems in setting the ovens for a production run.
To better determine optimal temperature settings and maintain existing or known settings without the need for test boards, electronic data loggers (also called data collectors) have been developed that mount to a test PCB. The test PCB has various thermocouples strategically placed thereon, which the data logger monitors. Using the data loggers, the optimal temperature of the oven can be determined. However, known data loggers have not been used to track overall oven performance, primarily because the focus of data loggers is on measuring the temperature of the product passing through the oven, not the oven itself. Additionally, known data loggers do not adequately track temperature as a function of position in the oven. Although temperature data can be collected, it is difficult to determine at what points or location in the oven the temperature data was collected.
Some companies have attempted to track oven performance by mounting a grid of thermocouples throughout the oven. If oven temperatures change over time, the user can detect these changes and take corrective action. However, the oven temperature is not the only factor in overall oven performance. The amount of air flow in the oven is also a factor in how the oven heats products. For example, many ovens (e.g., convection ovens) use forced air to heat products. Products heated in a convection oven heat more quickly than the same products heated in a standard (non-convection) oven. Consequently, reduced or increased air flow can also degrade oven performance, and temperature monitoring devices are incapable of monitoring such a degradation.
Accordingly, an object of the present invention is to provide an apparatus and method for accurately profiling oven performance. A further object is to provide such an apparatus and method that take into account both air temperature and air flow. A further object is to provide such an apparatus and method that can accurately correlate temperature data to positions within the oven. Still a further object is to provide such an apparatus and method that are easy to use and convenient.